Replace the startup gamma with the same from the standalone version

Fixes https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=629470

backend/hp3900_sane.c

@@ -1159,7 +1159,7 @@ options_init (TScanner * scanner)
       TOptionValue *pVal;
 
       /* set gamma */
-      gamma_create (scanner, 2.2);
+      gamma_create (scanner, 1.0);
 
       /* color convertion */
       scanner->cnv.colormode = -1;